Hardness testing machine



Jan. 4, 1944. L PODESTA 2,338,537

HARDNESS TESTING MACHINE Filed Feb. 26, 1940 3 Sheets-Sheet 1 Z'Smaentor,(Iss 7: Wodesiw Jan. 4, 1944. L. P. PODESTA 2,338,537

HARDNESS TESTING MACHINE Filed Feb. 26, 1940 3 Sheets-Sheet 2 3nventor u7;? y (Ittornegs Jan. 4, 1944. L. P. PODESTA 2,338,537

HARDNESS TESTING MACHINE Filed Feb, 26, 1940 3 Sheets-Sheet 3 Ennenfor55 Z? pociwf zz (Ittomegs Patented Jan. 4, 1944 UNITED STATES, PATENT mmIClalm.

chines and more particularly to machines for test ing the hardness ofgrinding wheels-and the like A common method of testing grinding wheelsfor hardness is the hand method. In this-method the one doing thetesting uses a tool shaped like a screw driver which is pressed againstthe grinding wheel to be tested and twisted by hand back and forth. Inthis way the amount of pressure required to release the grain from thebond vis determined. It is necessary for the tester to compare the wheelto be tested against a standard or master wheel. By forcing the screwdriver against the master wheel and twisting the hand, and then doingthe same with the wheel being tested a comparison between the two can beobtained. The results depend on the skill of the man doing the testing.

In an attempt to obviate the disadvantages of the hand method certainmachines have been heretofore proposed. These have been slow inoperation and have presented little, if any, advantages over the handmethod. For this reason the prior art machines have not been used to anygreat extent so far as I am aware, and the hand method is stillcommonlyemployed.

The primary objects of my invention are to provide an apparatus ormachine for testing grinding wheels and the like that eliminates thedisadvantages of the hand method, and to provide a hardness testingmachine that is characterized by speed, accuracy and ease of operationas compared with the prior art machines.

Reference is herewith made to the accompanying drawings forming aportion of this specification and illustrating preferred embodiments ofmy invention.

Figure 1 is an elevational view with parts broken away of a hardnesstesting machine in accordance with my invention.

Figure 2 is a view substantially on line 22 in Figure 1. v

Figure 3 is a view generally similar to Figure 1 of a modified form ofhardness testing machine in accordance with my invention.

Figure 4 is a view on line 44 in Figure 3.

In the form of the invention shown in Figures 1 and 2 the grinding wheelill to be tested is placed on a table i2. The table i2 is movableup anddown by means of lever [4 having a pinion i6 fixed to one end thereof,the pinion engaging a rack portion I8 of a post 28 which supports thetable l2. A handle 22 actuates a clamping means to lock the post andtable carried thereby in the desired position.

Mounted above the table in the overhanging portion of the frame 24 is aspindle 26 to which is secured at the-lower end thereof a tool 28. Anysuitable form of tool may be used, the form illustrated beingrectangular in cross-section and being somewhat similar to the blade ofa screw driver.

Fixed to the spindle 26 intermediate the upper and lower ends thereof isa collar 88. The collar is above the flange 82 of a slide 84. The slideis normally forced downwardly by means of suitable weights 36 carried bythe free end of a rope or flange 82 and on a shoulder 48 formed by anenlarged portion of the spindle is a roller thrust bearing 42.

Near the upper end of the spindle 26 and carried thereby is a Woodruifkey 44 having a por. tion thereof in slidable engagement with a splinedportion 46 of a sleeve or hub member 48 to which is fixed at its upperend a gear 58. The sleeve member 48 and the gear are mounted foroscillatory movement in a flanged sleeve 52 supported by the overhangingportion of the frame. The sleeve member 48 has a channel-shaped groove64 extending entirely around its circumference. A screw threaded pin 56projects into the groove through an opening 58 in the flanged sleeve 62.This fixes the splined sleeve 48 and gear 50 against longitudinalmovement with respect to the-supporting sleeve 52, but permits the gearand splined sleeve to oscillate back and forth by means later described.

Resting on the upper end of the spindle 26 is a.

rod 68 which projects above the gear 50 and contacts a rod actuatingmeans 62 of an indicator 64 carried by a bracket 66 fixed to'the upperportion of the frame. The pointer of the indicator is indicated at 61.

Supported by another bracket 68 carried by the frame is an electricmotor 18. Through a suitable speed reducing mechanism indicatedgenerally at I2 the motor drives a rotary member 14. A connecting rod 16is connected at one end to a pin 78 fixed to the rotary member 14 at apoint spaced from the axis of rotation. The opposite end of theconnecting rod is pivotally connected at 80 to a rod 82 having screwthreaded engagement with a rack 84, the teeth of the rack being inengagement with the teeth of the gear 68. The reciprocatory movement ofthe rack thus oscillates the gear and parts actuated thereby. The bodyof the rack is T-shaped in cross-section, the head of the T beingsupported for reciprocatory movement in a groove or channel formed by acut-away portion of a member 80 and removable strip plates 88 and 00. Iidesired, a counter mechanism indicated at 9| may be provided.

Preferably the motor controls are such that the motor'will stopautomatically after a predetermined time or predetermined number ofreciprocations or the rack. In this way the same number of oscillationsof the spindle and tool carried thereby can be had automatically foreach wheel being tested. One way of doing this is to provide the countermechanism with switch contacts which will open and break the current tothe motor after a predetermined number of reciprocations.

The method of operation of the hardness tester disclosed in Figures 1and 2 may be summarized as follows: The operator places a grinding wheelto be tested on the table I2 and raises the table and grinding wheeluntil the grinding wheel contacts the tool 28 carried by spindle 26.Further movement raises the spindle, slide 34, weights 35, rod 60, andthe indicator actuating means. The splined sleeve or hub 48 per-' mitsrelative movement between the hub and spindle. The movement is continueduntil the pointer of the indicator is moved to a predetermined point onthe scale of the indicator in the range'of hardness desired, whereuponthe table is locked in position.

The size of the weight is so chosen as to force the tool into the masteror standard grinding wheel a certain distance during a definite numberof oscillations of the tool. The tool will penetrate all wheels ofsimilar hardness an equal amount. The dial of the indicator can becalibrated to indicate the degree of penetration. Preferably differentsized weights are used for wheels having difl'erent hardnesses. Thus thelargest weight will-be used for the hardest grinding wheel, the smallestweight for grinding wheels of the softest range, and an intermediateweight for grinding wheels of intermediate hardness.

The motor is then started and by means of the speed reducing means therotary member I4 is rotated at a desired speed, preferably considerablyslower than the speed of rotation of the electric motor. The rotarymovement of member I4 is translated into reciprocatory motion to movethe rack 84 back and forth, thus oscillating the gear 50, which in turnmoves the spindle 20 and tool 28. The number of reciprocations of therack is fixed so that each wheel is given the standard test. Theoscillatory movement causes the tool to move into the grinding wheel acertain amount depending on the hardness of the grinding wheel beingtested. If the master grinding wheel, the wheel being tested is harderthan the standard.

In Figures 3 and 4 is shown another embodiment of the invention. In thisform the table, elevating mechanism for the table and table lockingmeans are not shown as they are similar to those provided in the form ofthe invention of Figures 1 and 2. 1n Figures 3 and 4, l0 represents thegrinding wheel to be tested. Above the grinding wheel is a tool 28'carried by a spindle 20'. The spindle is mounted within a flanged sleevemember 52' carried by the upper part of the frame 24'. Resting on aninwardly extending flange I00 01' the sleeve member 52' is an enlargedportion I02 of the spindle 20'. A coil spring I04 having one end restingon the upper side of portion I02 and its other end contactlng the lowerend of a sleeve member normally biases the enlarged portion of thespindle into engagement with the flange I00. The sleeve 48' is splinedat 40' and is connected by means of a Woodrufl key 44' with the spindle26'. Contacting the upper end of spindle 26' is a rod which extendsupwardly through the hub and engages an actuating means 62' for anindicator 64' having a hand or pointer 61'. A coil spring I06 biasesthe. rod 60' into pressure contact with the upper end of spindlegrinding wheel to be tested has the same hardness as that of the masteror standard wheel, the tool willmove into the grinding wheel to the samedepth as it does when the standard or master grinding wheel is similarlytested. The dial of the indicator is first calibrated with the master orstandard wheel. Grinding wheels having the same hardness as the masterwheel thus will have the same dial reading. If the tool moves deeperinto the grinding wheel as indicated on the dial of the indicator, thegrinding wheel is of a softer grade than the standard or master grindingwheel, while if the tool does not move as far into the grinding wheelbeing tested as it does in the case of the test on the 25'. Fixed to theupper end of the sleeve 48' is a gear 50' having engagement with theteeth of a rack 84', the rack being reciprocated by means ofscrew-threaded rod 82', connecting rod I6, pin I8, rotary member I4,speed reducing means I2 and electric motor I0.

In the lower end of sleeve 52' and having screw-threaded engagementtherewith is an adjustable stop I08.

- The operation of the modification of the invention shown in Figures 3and 4 is generally similar to that of Figures 1 and 2. The table andgrinding wheel to be tested are first moved to bring the grinding wheelinto contact with the tool 28'. Further movement causes the spindle tomove relative to the sleeve 48', thus' compressing coil springs I04 andI08 and moving the pointer oi the indicator to a desired pointed thedial. The stop I08 may be adjusted to contact the upper side of thegrinding wheel when the proper position is reached. The electric motoris started and the spindle and tool oscillated back and forth for apredetermined number of cycles, the compressed springs causing the toolto feed into the grinding wheel an amount dependent on the hardness ofthe grinding wheel.

It will thus be seen that in both of the embodiments of my inventiondisclosed herein that the spindle and tool are positively oscillatedback and forth by means or the electric motor reciprocating the rack fora desired number of cycles, the connection between the spindle andsplined sleeve permitting relative longitudinal movement between theseparts so that the loaded spindle and tool may move downwardly into thegrinding wheel an amount dependent on the hardness of the grinding wheelbeing tested.

Various changes in the embodiments of my invention disclosed herein maybe made without departing from the spirit and principles of my inventionand I do not intend to limit the patent granted thereon except asnecessitated by the prior art.

I claim:

In a machine for testing the hardness of grinding wheels and the like, awork support, a

; reciprocating the rack to oscillate back and forth means for applyinga load to the spindle and tool,

a gear fixed to the upper end of the sleeve, a reciprocatory rackengaging said gear, means for the gear, sleeve, spindle and tool whilethe load is applied to the spindle and tool to cause the tool topenetrate the work to a depth dependent on the hardness of the workbeing tested, an indicator above the gear and spindle for measuring thedepth of penetration of the tool into the work being tested, and aslidable rod for actuating the indicator passing through the gear andthrough the upper portion of the sleeve thereby engaging the upper endof the spindle and operating the indicator.

LEE P. PODESTA.

